Disposable foot covering

ABSTRACT

A DISPOSABLE FOOT COVERING COMPRISING A PAIR OF SUPERIMPOSED LAYERS OF FILM OR SHEET MATERIAL MARGINALLY SEALED TOGETHER, THE UPPER OF SUCH LAYERS BEING FORMED OF A HIGH ELONGATION ELASTOMER FILM AND BEING PROVIDED WITH A SMALL BUT GREATLY EXPANDABLE OPENING FOR THE INSERTION OF A WEARER&#39;&#39;S FOOT. A FUSED MARGINAL BEAD ABOUT THE OPENING PREVETS TEARING AS THE MATERIAL ABOUT THE OPENING IS STRETCHED. BREATHABILITY OF THE COVER, WHERE NECESSARY, IS INSURED BY FORMING THE COVER&#39;&#39;S LOWER LAYER FROM A POROUS MOISTURE-RESISTANT FILM OR SHEET.

Sept. 20, 1971 F. c. MOORE em 3,605,291

DISPOSABLE FOOT COVERING.

Filed July 27. 1970 IN'IORSJ I6 FRANCIS C. MOORE LEON R. PERKINSON 0(1137, awn/ug United States Patent Ofiice 3,605,291 DISPOSABLE FOOTCOVERING Francis C. Moore and Leon R. Perkinson, Indianapolis,

Ind., assignors to Moore-Perk Corporation, Indianapolis, Ind.

Filed July 27, 1970, Ser. No. 58,404 Int. Cl. A43b 3/16 US. Cl. 367.1R21 Claims ABSTRACT OF THE DISCLOSURE A disposable foot coveringcomprising a pair of superimposed layers of film or sheet materialmarginally sealed together, the upper of such layers being formed of ahigh elongation elastomer film and being provided with a small butgreatly expandable opening for the insertion of a wearers foot. A fusedmarginal bead about the opening prevents tearing as the material aboutthe opening is stretched. Breathability of the cover, where necessary,is insured by forming the covers lower layer from a porousmoisture-resistant film or sheet.

BACKGROUND Despite considerable effort in the past to develop disposableshoe covers suitable for use by surgeons, nurses, and others, priorproducts have all been found to have major shortcomings. For example,paper shoe covers are commonly used and have the advantages of low cost,disposability (by incineration), and breathability. However, such coversdo not normally fit snugly over a wearers shoes without some additionalmeans (such as tie bands or elastic bands) which are designed to take upslack and which require additional manipulation by a user when thecovers are donned. Furthermore, paper tears easily and, because of itsporosity, offers only limited protection against penetration by fluids.

In our prior Pat. 3,442,034 we have disclosed an improved shoe coverformed largely of plastic foam. While the sole of such coverincorporates a non-porous moisture barrier, the top layer was leftporous in order to achieve a breathable product which could be worn forextended periods in surgery without discomfort to the wearer. Because ofsuch porosity, however, the foam top layer provides only limitedprotection when exposed to liquids. Furthermore, such liquids, many ofwhich may be contaminating and dangerous, might readily contact awearers foot because of the gaps created by the top opening of the coverwhich must be relatively large to permit insertion of a wearers footwithout causing tearing of the foam upper layer.

SUMMARY It is an object of one form of the present invention to providea shoe cover which is breathable and is therefore comfortable to wearindoors for extended periods, and yet one which has a top barrier layerwhich fully covers the top of a wearers foot and which will block thepenetration of liquids impinging on that layer. It is a specific objectto provide a shoe or foot covering which is easily fitted upon a wearsfoot and which fits snugly over the foot and about the wearers anklewithout the use of ties, elastic bands, or the like. The result is aninexpensive disposable shoe or foot cover which aifords ampleprotection, is comfortable to wear, and, in general, overcomes thedefects and disadvantages of prior constructions.

In accordance with this invention, a disposable foot covering isprovided including a top layer of a nonporous thermoplastic elastomerhaving a modulus of elongation of at least about 300 percent, such layerbeing 3,605,291 Patented Sept. 20, 1971 marginally sealed to a bottomlayer of the same or different material and having an opening in the toplayer that is relatively small in relation to the surface area of suchlayer by a ratio of about 1:10. A tear resistant bead extends about theopening to prevent tearing of the top layer despite the extensivestretching of the material about the opening as a foot is inserted intothe cover. By forming the lower layer of a tough compatible sheetmaterial which is porous and is therefore permeable to air (butresistant to the passage of liquids), a covering is provided which isparticularly effective for use in surgery and elesewhere. In a preferredform of the invention, the lower layer is formed of a tough andrelatively non-stretchable material; however, despite suchnon-stretchability of the lower layer, the cover fits snugly and iscomfortable to wear, without the joined edge portions of the upper andlower layers extending beneath a wearers foot and causing objectionableridges (which might also interfere with good electrical grounding shoulda conductive strip be provided) because of the elasticity of the upperlayer and the size of the cover relative to the area defined by theoutline of a wears foot.

DRAWINGS FIG. 1 is a perspective view of a covering embodying theinvention, such covering being illustrated upon a wearers foot;

FIG. 2 is a top plan view of the covering;

FIG. 3 is a somewhat schematic sectional view taken along line 33 ofFIG. 2;

FIG. 4 is an enlarged view illustrating the bead and opening forming theoperation.

DESCRIPTION In the illustration given, the numeral 10 generallydesignates a foot covering having a pair of flat superimposed upper andlower sheets of layers 11 and 12, respectively. The layers are of thesame size and, as illustrated most clearly in FIG. 2, are generally ovalor almond-shaped in configuration. Each of the layers has a surface areasubstantially larger than the area defined by the outline of wearersfoot; specifically, the area of each layer should be approximately 30 topercent greater and the margins of the layers should extend Well beyondthe margins or limits of the foot upon which the cover is to be fitted.

While the covering is referred to herein as a foot covering, it is to beunderstood that the product would ordinarily be worn over a wearersshoes. Under those circumstances, the terms foot and shoe are usedinterchangably herein. Thus, in speaking of the differential in areabetween the outline of the covering and the outline of a wearers foot,the term foot should be understood to mean shoe in those instances wherethe covering is to be worn over a shoe. Such usage is illustrated in thedrawings with the foot outline 13 in FIG. 3 actually being the outlineof the sole and heel of a wearers shoe, such shoe being designated bythe numeral 14 in FIG. 1.

The top layer or sheet 11 is formed of a non-porous high-elongationthermoplastic elastomer. Such elastomer should be capable of at least300 percent, and preferably 500 percent, elongation. While variousplastic materials might be used, particularly effective results havebeen obtained with films formed of block copolymers of styrene andbutadiene. Elastomeric films of polyurethane may also be used.

A relatively small ankle opening 15 is provided in top layer 11. Theopening is defined by a continuously curved edge in either circular oroval configuration and is substantially smaller (when the layer is in anuntensioned state) than the dimensions of a wearers ankle. Depending onthe foot size of the intended wearer, the

area of opening 15 should fall within the range of approximately 1 to 4square inches and, in any event, should be no greater than one tenth thearea defined by the outline of the cover as a whole. For a coveringadapted to be fitted over the foot of an adult, particularly effectiveresults have been obtained where the area of opening 15 falls within therange of 1.5 to 3.0 square inches.

While lower layer 12 may be formed of the same material, the advantagesof the invention are more completely realized if such layer is formedfrom a material which, in addition to being strong, tough and pliable,is also porous. Such porosity permits the flow of air through the coversto prevent the buildup of heat and moisture which would otherwise renderthe covers uncomfortable to wear for the extended periods that arefrequently encountered in surgery, etc. At the same time, such materialshould byeither treatment or composition be resistant to the passage ofliquids therethrough. While tough paper materials which have beentreated to be liquid resistant may be used, porous plastic materialssuch as spun-bonded polyethylene have been found especially effective.

The superimposed layers have their marginal portions secured together byheat sealing or lay any other suitable means. Heat sealing isparticularly advantageous because the integrity of non-porous characterof the upper layer 11 is thereby maintained; however, somewhat similarresults might be achieved by utilizing a suitable cement or adhesive tobond the edges of the layers together or by sewing or otherwise securingthem to each other.

In the illustration given, a flexible strip 16 is secured byheat-sealing, adhesive, or stitching to the undersurface of bottom layer12 along the longitudinal midline thereof. Preferably the conductivestrip is composed of a fabric-reinforced foil which has been foldedlongitudinally as illustrated in FIG. 3, such strip being fabricated asdisclosed in our co-pending application, Ser. No. 58,403, filed July 27,1970. The strip has a free end portion 16a which projects beyond therear end of the cover and which is intended to be brought into contactwith a wearers leg or foot. Thus, the end portion of the conductivestrip may be tucked in the opening of a wearers sock or shoe to providean electrically conductive path for preventing static buildup inlocations where a spark or static discharge might ignite explosive gasesor highly combustible fluids.

Because of the dimensions of the cover and the elasticity of upper layer11, the sealed edge portion 17 of the cover tends to be pulled upwardlyout of contact with a floor surface when the foot cover is worn (FIG.1). The double-thickness edge portion 17 is therefore displaced awayfrom beneath the foot where such increased thickness might otherwiseinterfere with proper contact between conductive strip 16 and a floorsurface. Stated differently, the size of the cover and the tension ofupper layer 11 when the cover is worn insure that conductive strip 16will be exposed for direct and forceful contact with a floor surface andthat the marginal zone 17 of double thickness will not interfere withthat contact.

Despite the substantial tension imposed on upper layer 11 when the coveris worn, the edge of opening 15 fits snugly about the wearers ankle 19.Thus, as illustrated in FIG. 1, a wearers shoe is completely covered. Ofparticular importance in achieving a snug fit about the ankle is theespecially small size of opening 15 when the upper layer is in anuntension state. Even though the upper layer must undergo substantialstretching and tensioning when the cover is worn, such tensioning doesnot increase the size of the opening to the point where a snug fit andadequate protection are lost.

FIG. 3 illustrates that a bead or marginal enlargement 15a is providedabout opening 15. At the time that the opening is cut into the upperthermoplastic layer 11 uring fabrication of the cover, the cutting blade18 is heated to produce retraction and fusion along the edge. Nicks orslight irregularities of even microscopic size, which might otherwise bethe starting points of tearing when the opening is later stretched overa wearers foot, are thereby eliminated. In addition, the enlargeheat-retraction bead 15a provides reinforcement for the edge because ofits increased thickness. FIG. 4 illustrates in somewhat schematicfashion the manner in which the material retracts to form thereinforcing head when the opening 15 is cut by hot knife 18.

The temperature of the knife will of course vary depending upon thematerial being cut and the duration of the cutting step. In general, ithas been found that if the blade is heated to approximately the melttemperature of the thermoplastic material and is in contact with thefilm no longer than approximately one second then an effective bead 15awill be formed. Higher temperatures may be used if the interval ofcontact is shorter and somewhat lower temperatures may be used forlonger contact periods.

From the foregoing, it is believed apparent that the article of thepresent invention constitutes a highly effective foot covering which isespecially suitable for use by surgeons, nurses, etc. The wearer isprotected against contamination by liquids often present during surgerybecause of hte non-porous liquid-impermeable material of upper layer 11and because of the snug fit of opening 15 about the wearers ankle.Nevertheless, the cover is comfortable to wear, even for extendedperiods, because of the air permeability of the sole or bottom portion12. Comfort is also increased because of the tensioned fit of the coveras a whole resulting from the stretched and tensioned nature of the toplayer when the cover is worn. In that connection, it is to be observedthat the tensioning of the upper layer or sheet 11 will result in a snugcomfortable fit of any given cover over a range of shoe sizes.

In general, a foot covering embodying the present invention, constructedas described above, may be formed where the upper layer 11 is formed ofa thermoplastic elastomer exhibiting the following properties.

Property: Value Tensile strength, p.s.i 625-3000 300% modulus, p.s.i200-970 Elongation, percent 300-1350 Hardness, shore A 35-77 Tearstrength -460 Specific gravity 0.93-1.02

The invention is further illustrated by the following specific examples:

EXAMPLE I A shoe cover embodying the invention may be made utilizing forthe upper layer of film of 4 mil (0.004 inch) in thickness of abutadiene-styrene copolymer marketed under the trademark Kraton 2109 byShell Chemical Company, New York, N.Y. To fit size 9-11 shoe, theoutline of the cover defined an area of approximately 83 square inchesand the area of the ankle opening in the untensioned upper layer wasapproximately 3 square inches. The lower layer was formed of spun-bondedpolyethylene marketed under the designation Tyvek by E. I. du Pont deNemours, Wilmington, Del., and the two layers were heat sealed togetherabout the periphery of the cover. A conductive strip offabric-reinforced aluminum foil was adhesively secured to the undersideof the cover along the longitudinal midline thereof.

EXAMPLE II Another cover embodying the invention may be formed utilizingthe porous spun-bonded polyethylene described in Example I for thebottom layer and using for the upper layer an elastomeric polyurethanefilm marketed under the designation Tuftane by B. F. Goodrich ChemicalCompany, Cleveland, Ohio.

EXAMPLE 1 11 As a further illustration of the invention, a shoe covermay be formed utilizing for the upper layer a film of 3 mil (0.003 inch)in thickness of the butadienestyrene copolymer identified in Example Iand using for the bottom layer a scrim-reinforced paper marketed underthe designation Kaycel by Kimberly-Clark Corporation, Neenah, Wis. Thelayers of the cover may be heat sealed together and the cover may beotherwise formed as described in Example I. Because of the porosity ofthe soft reinforced paper bottom layer, such cover is breatheable andcomfortable to wear despite the non-porous character of the top layer.

In the preceding description and examples, the shoe covers embodying theinvention have been characterized as having upper layers of a non-porousand highly stretchable thermoplastic elastomer to protect the surgeon,nurse, or other wearer against contaminating contact with spilledliquids while, at the same time, because of the porosity of the lowerlayers, such covers provide for breathability and wear comfort. It is tobe understood, however, that where such protection against possiblecontamination or injury from spilling liquids is not required, the upperlayers might be provided with small vents or openings to furtherincrease the circulation of air through the covers.

While in the foregoing We have disclosed embodiments of the invention inconsiderable detail for purposes of illustration, it will be understoodby those skiled in the art that many of these details may be variedwithout departing from the spirit and scope of the invention.

We claim:

1. A protective foot covering comprising a pair of flat superimposedupper and lower sheets having curved peripheral edges defining an areaapproximately 30 to 100 percent larger than that defined by the outlineof a wearers foot; said upper sheet being formed of an essentiallynon-porous and high-elongation thermoplastic elastomer having at least300 percent elongation and said lower sheet being formed of a toughporous moisture-resistant material; the peripheral edge portions of saidsheets being sealed together to define a space between said sheets forreceiving a wearers foot; said upper sheet having an opening therein forinsertion of a wearers foot into said space; said opening when saidupper layer is untensioned having an area less than one tenth the areadefined by the outline of said superimposed sheets.

2. The foot covering of claim 1 in which said sheets are of the samesize and are generally oval in shape.

3. The foot covering of claim 1 in which said lower sheet is relativelynon-stretchable.

4. The foot covering of claim 1 in which said upper and lower sheetshave their peripheral edge portions heat sealed together.

5. The foot covering of claim 1 in which said opening is defined by anedge of generally continuous concave curvature, that opening beingdefined by an edge having an enlarged heat-fused bead.

6. The foot covering of claim 1 in which said upper sheet is formed froma butadiene-styrene copolymer.

7. The foot covering of claim 1 in which said upper sheet is formed froma urethane film.

8. The foot covering of claim 1 in which said lower sheet is formed ofspun-bonded polyethylene fibers.

9. A protective shoe cover for use in surgery comprising a pair of flatsuperimposed upper and lower sheets having an outline defining an areaapproximately 30 to 100 percent larger than the outline of a wearersshoe; said upper sheet being formed of an essentially non-porous andhigh-elongation thermoplastic elastomer having at least 300 percentelongation; said lower sheet being formed of a tough, porous,moisture-resistant, and relatively non-stretchable material capable ofbeing heat sealed to said upper sheet; said upper and lower sheetshaving their peripheral edge portions heat sealed together along theirentire extent; said upper sheet having an opening therein defined by anedge of concave curvature and having an area when said upper sheet isuntensioned of less than one tenth the area defined by the outline ofsaid superimposed sheets; and a conductive strip secured to theunderside of said lower sheet and having an end portion adapted to beplaced in conductive contact with a wearer.

10. The shoe cover of claim 9 in which said sheets are of substantiallythe same size and are generally oval in shape.

11. The shoe cover of claim 9 in which said upper and lower sheets havetheir peripheral edge portions heat sealed together.

12. The shoe cover of claim 9 in which said opening is defined by anedge having an enlarged continuous heatfused bead.

13. The shoe cover of claim 9 in which said upper sheet is formed from abutadiene-styrene copolymer.

14. The shoe cover of claim 9 in which said upper sheet is formed from aurethane film.

15. The shoe cover of claim 9 in which said lower sheet is formed ofspun-bonded polyethylene fibers.

16. A protective foot cover comprising a pair of flat superimposed upperand lower layers having curved peripheral edges defining an area atleast 30 percent larger than that defined by the outline of a wearersfoot; said upper layer being formed of an essentially non-porous andhigh-elongation thermoplastic elastomer having at least 300 percentelongation and said lower layer being formed of a thermoplastic materialcapable of being heatsealed to said upper layer; the peripheral edgeportions of said upper and lower layers being heat-sealed together alongtheir entire extent; said upper layer having an opening of roundedoutline therein for insertion of a wearers foot between said upper andlower layers; said opening when said upper layer is untensioned havingan area no greater than one tenth the area defined by the outline ofsaid superimposed sheets.

17. The foot cover of claim 16 in which said opening is defined by athickened continuous bead formed integrally with said upper layer.

18. The foot cover of claim 16 in which said opening is generally ovalin outline.

19. The foot cover of claim 16 in which said lower layer is formed of anon-porous high-elongation thermoplastic elastomer having at least 300percent elongation and capable of being heat-sealed to said upper layer.

20. The foot cover of claim 16 in which said lower layer is formed of atough porous moisture-resistant thermoplastic material.

21. The foot cover of claim 20 in which said lower layer is formed ofspun-bonded polyethylene fibers.

References Cited UNITED STATES PATENTS 3,308,562 3/1967 Zimmon 367.1R3,359,658 12/1967 Price 36-7.1R

PATRICK D. LAWSON, Primary Examiner US. Cl. X.R. 3 17-2 (5/69) UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,605,291Dated September 20, 1971 Inventor-(s) Francis C. Moore and Leon R.Perkinson It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Claim 1, line 6, the word "thermoplastic" should be deleted.

Claim 4, line 1, after "said" insert upper sheet is formed of athermoplastic elastomer, said Claim 5, line 1, after "said" insert uppersheet is formed of a thermoplastic elastomer, said line 2, delete "is"and substitute being Signed and sealed this 21 st day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents

